Search Results for microstructure development

This article discusses the metallurgical aspects of underwater welds. It describes the microstructural development, which mainly includes three types of ferrite associated with low carbon steel weld metal: grain-boundary ferrite, sideplate ferrite, and acicular ferrite. The article explains the factors that affect heat-affected zone (HAZ) cracking. These include hydrogen from the weld pool, microstructures that develop in the HAZ, and stress levels that develop in the weld joint. The article describes the welding practices that can reduce residual stresses. It explains the effect of water pressure on the formation of porosity in underwater gravity welding. The article concludes with a discussion on the practical applications of underwater welding.

Conventional high-strength aluminum alloys produced via powder metallurgy (P/M) technologies, namely, rapid solidification (RS) and mechanical alloying (mechanical attrition) have high strength at room temperature and elevated temperature. This article focuses on the metallurgy and weldability of dispersion-strengthened aluminum alloys based on the aluminum-iron system that are produced using various RS-P/M processing techniques. It describes weldability issues related to weld solidification behavior, the formation of hydrogen-induced porosity in the weld zone, and the high-temperature deformation behavior of these alloys, which affect the selection and application of fusion and solid-state welding processes. The article provides specific examples of material responses to welding conditions and highlights the microstructural development in the weld zone.

This article provides information on the base material properties of wrought duplex stainless steels (DSS). These properties include microstructure, alloy grades, mechanical and physical properties, and corrosion resistance. The article reviews the applications and microstructural development of DSS. It describes the factors influencing welding and weldability of the DSS. These factors include preheating, postweld heat treatment, interpass temperature control, welding practices, welding procedure qualification, filler metal requirements, cracking behavior, and loss of properties. The article examines the applicable welding processes such as fusion welding and solid-state welding processes.

This article discusses the properties of aluminum surface and the applications of aluminum alloys. It explains the effects of trace elements on aluminum alloys. The article considers microstructural development of aluminum in terms of the surface and explains how it will impact corrosion resistance and surface treatment. It describes the thermodynamics of equilibrium oxidation processes and non-equilibrium corrosion processes. The article provides a discussion on aluminum oxidation under atmospheric and dynamic conditions. It presents the potential/pH (Pourbaix) diagram for aluminum under atmospheric and dynamic conditions. The article also explains the polarization effects during the formation of stable aluminum oxide under dynamic conditions. It concludes with information on the designation system for aluminum finishes.

This article discusses two major sintering methods: pressureless and pressure-assisted sintering. Pressureless sintering techniques include vacuum and partial-pressure, hydrogen, and microwave sintering. Pressure-assisted consolidation techniques include overpressure sintering, sintering followed by postsinter hot isostatic pressing, hot pressing, and several rapid hot consolidation techniques. The article describes nitrogen sintering and the sintering of cermets. It reviews the furnaces used for sintering and presents the lubrication removal techniques. The article also outlines the need to control carbon and oxygen to obtain optimal properties and explains microstructure development and grain size control.

This article focuses on friction stir welding (FSW), where frictional heating and displacement of the plastic material occurs by a rapidly rotating tool traversing the weld joint. Much of the research activity early on pertained to issues related to understanding the process, such as learning about material flow, heat generation, microstructure development, and many other fundamental issues. The article summarizes the results of the research, describing the aspects of how FSW actually accomplishes sound joints in metals without melting them. It discusses the FSW process variations and the practical aspects of heat generation. The article provides information on the effect of welding on material properties and typical alloys in FSW applications. The alloys include 6061 aluminum, 5083 aluminum, 2xxx aluminum, and 7xxx aluminum alloys. The article concludes with a discussion on FSW equipment.